Rating:
[Details](https://github.com/nevivurn/writeups/tree/master/2018-isitdtu/XOR)
```python
#!/usr/bin/env python2
enc_flag = '1d14273b1c27274b1f10273b05380c295f5f0b03015e301b1b5a293d063c62333e383a20213439162e0037243a72731c22311c2d261727172d5c050b131c433113706b6047556b6b6b6b5f72045c371727173c2b1602503c3c0d3702241f6a78247b253d7a393f143e3224321b1d14090c03185e437a7a607b52566c6c5b6c034047'
keylen = 10
def unshuffle(m):
unshuf = [None]*len(m)
ind = 0
for a in range(keylen):
i = a
for b in range(len(m)/keylen):
if b % 2 != 0:
unshuf[i] = m[ind]
else:
unshuf[i + keylen-(a+1+a)] = m[ind]
i += keylen
ind += 1
return unshuf
enc_flag = [ord(c) for c in enc_flag.decode('hex')]
keyind = []
for i in range(keylen):
keyind += [i] * (len(enc_flag)/keylen)
enc_flag = unshuffle(enc_flag)
keyind = unshuffle(keyind)
plain = 'ISITDTU{We'
keys = []
for off in range(len(enc_flag)-len(plain)):
key = [None]*keylen
for i,p in enumerate(plain):
k = enc_flag[off+i] ^ ord(p)
if key[keyind[off+i]] == None:
key[keyind[off+i]] = k
elif key[keyind[off+i]] != k:
break
if key.count(None) == keylen-len(plain):
keys.append(key)
charset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_.!?@-{}'
for key in keys:
plain = ''
fine = True
for c, k in zip(enc_flag, keyind):
p = 0
if key[k]:
p = c ^ key[k]
if chr(p) not in charset:
fine = False
break
else:
p = ord('#')
plain += chr(p)
if fine:
print plain
```
